The aim of the proposed supplement to grant GM10422 is to continue the efforts begun in my laboratory 16 years ago to develop procedures for quantitative analysis of EM autoradiography. The main proposal approved last year outlined plans to calibrate and apply isotopes with higher energy than normally used in EM autoradiography such as 14C, 45Ca and 33P. The potential application of these isotopes to high voltage microscopy was considered as was the resolution and sensitivity obtained with track autoradiography, scintillator fluids and with the use of a dry stripping film for soluble compound autoradiography. The major aim of this supplemental application is to obtain funds for the purchase of a computer to expedite the performance of newly developed statistical procedures for analyzing autoradiograms.